Self-propelled sweepers or robotic vacuum cleaners that collect dust from the surface of a floor are known and include a built-in motor that rotationally drives its wheels. As disclosed, for example, in Japanese Unexamined Utility Model Application Publication No. H5-88472, such a sweeper may comprise a rotary brush that is rotated by the drive of a motor and is disposed forward of a suction port. The sweeper gathers or sweeps up dust from the surface of the floor using the rotary brush.